List placement groups

Example response

{
  "count": 1,
  "results": [
    {
      "instances": [
        {
          "instance_id": "6d14f194-6c1e-49b3-9fc7-50dc8401eb74",
          "instance_name": "my-instance-1"
        },
        {
          "instance_id": "142988bb-291e-4862-bffb-b1cf20036c27",
          "instance_name": "my-instance-2"
        }
      ],
      "name": "my-server-group",
      "policy": "anti-affinity",
      "project_id": 1337,
      "region": "Luxembourg 1",
      "region_id": 7,
      "servergroup_id": "47003067-550a-6f17-93b6-81ee16ba061e"
    }
  ]
}